Interesting, but I doubt that Halo 2 had any of that functionality working (sharing films, maps, etc.).
That looked like an animated UI mockup, probably done in Macromedia Director, to show an
example of what the UI might look like. It was probably done in pre-production before any of the code was even working, and they were thinking of adding those features (sharing, etc.) but hadn't yet implemented them.
Here's an article about how they used Director for quick and dirty mockups and prototypes of the UI:
http://www.adobe.com/devnet/director/articles/halo_ui.html